Explanation:
M4 is a
globular cluster visible in dark skies about
one degree west of the bright star
Antares in the constellationScorpius.
M4 is perhaps the closest
globular cluster at 7000
light years, meaning that we see
M4 only as it was 7000 years ago, near the dawn of recorded
human history.
Although containing hundreds of thousands of stars
and spanning over 50 light-years,
M4 is
one of the smallest and sparsest
globular clusters known.
A particularly unusual aspect for a globular cluster is
M4's
central bar of stars.
M4,
pictured above, is one of the oldest objects
for which astronomers can estimate age directly.
Cluster
white dwarfs appear to
be at least nine billion years old - so ancient they
limit the youth of our
entire universe.